Unit 2 Assignment

Functions and Testing
AP Computer Science 2021-22 / Dr. Kessner

Reading

• Eck Section 3.1 Blocks, Loops, and Branches (http://math.hws.edu/javanotes/c3/s1.html)
• Eck Section 3.5 The if statement (http://math.hws.edu/javanotes/c3/s1.html#control.1.3)
• Supplemental: Wikibooks Java (Statements, Conditional blocks, Loop blocks, Boolean expressions) https://en.wikibooks.org/wiki/Java_Programming

Coding Bat

Do these five exercises on Coding Bat Warmup 1 (http://codingbat.com/java/Warmup-1).

• diff21
• parrotTrouble
• makes10
• posNeg
• icyHot

Note: There is nothing to turn in for this part. These Coding Bat exercises are really good practice, so feel free to come back to them periodically.

Code

1. Choose two of the above Coding Bat exercises to implement and test on your own. Your class should include the function, a testing function, and multiple tests in main().

   For example, if you pick diff21, you should write a class named Diff21 in a file Diff21.java. The class should include a static function named diff21(), and a function named testDiff21(). You should call the test function on multiple inputs in main().

2. A person is a vampire if she is asleep during waking hours (6:00 to 22:00), or awake during sleeping hours (before 6:00 or after 22:00). Write a class with a static function boolean isVampire(float hour, boolean awake) where hour is the time represented as a float (e.g. 6.5 means 6:30), and awake represents whether the person is awake, returning true if that person is a vampire. Be sure to write a unit test function and a few tests.

3. A store has marked down the prices of many items, but you only want to buy something if the discount is more than 25% (or in other words, the sale price is < 75% of the original price). Write a function boolean goodDeal(double originalPrice, double salePrice) that returns true if you’re getting a good deal on the item. Be sure to write a test function and several tests.

Note: The Unit 2 Quiz will consist of problems similar to #2 and #3, but you will be asked to write code for only the specified function, not the testing function or unit tests.

Bonus Exercise

Write a program to print the prime numbers.

To do this, first write a function isPrime():

static boolean isPrime(int n)
{
    // return true <-> n is prime
}

Then in your main() function, loop through the first 100 integers and print only the ones for which isPrime() returns true.